3D printing is an Additive Manufacturing (AM) or Rapid Prototyping (RP) process of making a three-dimensional solid object of virtually any shape from a digital model. 3D printing is achieved using an additive process, where successive layers of material are laid down one on top of the other. 3D printing is considered distinct from traditional machining subtractive processes techniques which mostly rely on material removal by methods such as cutting or drilling.
Relevant prior art referencing the subject of the present invention comprise patents and patent applications as follows:
US 20080185365 A1, Flatbed Laser Engraver (use of QCL laser for engraving plastics);
U.S. Pat. No. 7,823,366 B2, Apparatus and Method for Selective Processing of Materials with Radiant Energy (focus on heat-shrinking polyethylene plastic on bottle containers using QCL) [see also: WO 2006069261 A2];
US 20120195335 A1, Device Comprising a Laser (industrial material processing); and
CN 200620166256 Platform-type Laser Carving Machine (focus on engraving).
Only recently 3D printing gained popularity as web-sharing and 3D printers became available and affordable by small businesses or enthusiastic home users. The great vision of producing “whatever you imagine” is still very limited due to low quality materials, low resolution, extremely slow printing speeds and cost of existing solutions.
There are two branches of 3D printing: polymers and metals. Polymers 3D printing is a widespread application. Prices range from over $1M to $1K per printer. Metal 3D printers are more of a specialty and so far remain at the high end of the market.
Current 3D printing systems suffer from many drawbacks. The majority of 3D printers today use photopolymer replacements for engineering plastic materials. These materials do not have the mechanical properties of the plastics they mimic. They have a different feel than the plastics they are supposed to replace and are very expensive. 3D printers that do use engineering plastics are mostly high end, expensive, low-resolution machines that use just one or two plastic materials from the vast array of possible plastics available. In recent years many low cost home enthusiasts 3D printers became available. They also use thermoplastics but their building quality is absolutely unacceptable for any functional purposes.
Another issue with current 3D printers is that they produce low resolution parts compared to other methods of manufacturing. Final parts do not look or feel as smooth as parts manufactured by mass production injection molding or even machining.
Finally, printing speed today is extremely slow—quite the opposite to the name ‘Rapid Prototyping’. An object may take many hours or even days to print.
There are several leading 3D printing technologies dominating the market today:                1. SLS—Selective Laser Sintering systems use a plastic powder bed and selective sintering by means of a CO2 laser beam (FIG. 2). Though the resulting models are made of engineering plastics (e.g. Nylon or ABS) the surface is very rough, small details are impossible to achieve due to poor CO2 laser resolution and building speed is low due to vector-type imaging. The machines are very expensive due to their physical size dictated by the CO2 optical path. The main manufacturers of machines of this type are 3D Systems and EOS (based in Germany).        2. SLA—Stereo Lithography Systems use UV laser for selectively curing layers of liquid photopolymer. UV lasers have a great optical quality and combined with a short wavelength allow fine resolution imaging. The resulting parts have good surface quality and fine details are obtainable. However the cured photopolymer has poor elastic and thermal quality making it impossible using the 3D printed parts as functional parts (e.g. miniature medical devices). The speed is also low due to vector imaging. The main manufacturers of machines of this type are 3D Systems, one of the earliest companies in the field of 3D printing and applications (333 Three D Systems Circle, Rock Hill, S.C. 29730, USA) and Envisiontec (Germany). DWS Lab (Zane, Italy) is an Italian manufacturer that specializes in high-end commercial laser 3D printers of the Laser Stereolithography process.        3. Inkjet Photopolymer is another way to produce 3D models by curing photopolymer layers. An array of inkjet nozzles images 2D slices of the model. A UV lamp cures the layer immediately after the imaging producing solids in imaged areas. The method was applied by Objet, recently acquired by Stratasys. Inkjet allows raster imaging and throughput scalability by increasing the number of nozzles. It produces resolution comparable to SLA though surface quality and the level of details remain worse than that obtained with SLA. Though the choice of materials offered by inkjet systems is impressive in its variety, none of them are truly functional due to the fact that these are still photopolymers with the same qualities as in SLA.        4. FDM—Fused Deposition Modeling (see FIG. 3—prior art) is based on a thermoplastic filament passing through a heated nozzle. The heat turns the plastic into soft paste. The nozzle moves in an X-Y plane, vector imaging each layer. A feed motor is responsible for pushing the filament down the nozzle in a controlled fashion. The method can produce models from engineering plastics. Its great advantage is system simplicity allowing drastic cost reductions. Some systems sell for under $1K. The drawbacks are low resolution and poor surface quality, inability to produce fine details, low throughput due to vector imaging and lack of speed scalability. The largest manufacturer for FDM systems is Stratasys whose focus is largely on industrial and commercial models. Their 3D printers are mainly used for rapid prototyping, parts production, and developing tools and jigs for fabricators.        
Quantum Cascade Lasers (QCLs) were invented in Bell Labs in the middle of the 90's. QCLs are typically small (5 mm long) semiconductor lasers which have the highest single mode power of any semiconductor single mode laser (up to 5 W). They are simple to operate using low cost electronics and can be easily modulated rapidly by the electric current.
QCLs operate in a fundamentally different way than CO2 lasers, such as in common use today.
Diode lasers are limited to about 2.5 μm wavelength because the wavelength is determined by the recombination energy, or bandgap, of the material system used to fabricate the device. Different material combinations result in different bandgaps, but there is a limit to the materials that can be used to make a diode laser.
Quantum cascade lasers are comprised of dozens of alternating layers of semiconductor material, forming quantum energy wells that confine the electrons to particular energy states. As each electron traverses the lasing medium it transitions from one quantum well to the next, driven by the voltage applied across the device. At precisely engineered locations, called the “active region,” the electron transitions from one band energy state to a lower one and in the process emits a photon. The electron continues through the structure and when it encounters the next active region it transitions again and emits another photon. The QCL may have as many as 75 active regions, and each electron generates that many photons as it traverses the structure.
Because QCLs emit in the mid- and long-wave IR bands, they are finding new applications in precision sensing, spectroscopy, medical, and military applications. Their wide tuning range and fast response time allow for faster and more precise compact trace element detectors and gas analyzers that are replacing slower and larger FTIR, mass spectroscopy, and photo-thermal micro-spectroscopy systems.
QCLs are most commonly made of layers of InGaAs and InAlAs on an InP substrate. The lasers wavelength region is very large from the IR to THz region (3-120 micron). Its main advantage in plastic processing applications is the ability to design and manufacture QCLs with specified wavelengths in the infrared region where plastics have their absorption peaks (see FIGS. 4, 5, and 6). These lasers lend themselves to several applications in plastic manufacturing and marking by removing, heating, melting or adding material.
Thus there is a need to overcome the disadvantages in prior art devices and methods for 3D printing technology in order to achieve a more efficient and accurate outcome in printing and manufacturing, especially in plastic materials and components. There is also a need to move beyond the use of the industry standard of CO2 laser technology in combination with 3D printing technology in order to broaden the scale and range of applications possible in the field.